The present invention relates to electrical wiring devices of the type which are used in industrial environments to provide connectors for electrical cables, and more particularly, to connectors which may be installed (i.e. attached to the wires of a cable) in the field, for example, to replace a defective or old connector.
Electrical wiring devices (primarily electrical power connectors) designed to be attached to a cable in the field and of commercial or industrial quality are required to have some means for gripping the cable to prevent stress from being transmitted to the connection itself in the event a user inadvertently seeks to disconnect the device by pulling on the cable rather than the connector body, as is the proper way to disconnect.
It is also desirable that the connectors be capable of being attached to a range of cable sizes. For example, the same device may be designed to be attached to cables having three insulated conductors. Each of the three conductors may be wire of a range of gauge, including 12, 14, 16 and 18 gauge wire. The strain relief mechanism must, of course, be effective with the entire design range of these wire sizes and outer diameter of the cable.
Some current commercial wiring devices provide strain relief by using a shim or spacer, sometimes referred to as a xe2x80x9cchickletxe2x80x9d which is inserted into the rear or cable end of the connector and used to adjust the size of a clamp opening to cables of smaller gauge wires, e.g. 16 and 18 gauge. Without the chicklet, the opening is sized to larger cables.
Another suggested approach disclosed in U.S. Pat. No. 5,304,075 includes a clamp attachable to an extension of a housing for a core, includes a series of concentric, spaced, closed cylindrical walls on the clamp in opposing relation to another series of cylindrical walls on the housing extension. The opposing cylindrical walls clamp down on the cable jacket to provide strain relief. Cables of a limited range of sizes may be accommodated.
Another aspect of present commercial electrical power connectors designed for installation in the field is that many use metal screws on the face of the core to secure it to the connector housing. The use of face screws to accomplish this purpose increases replacement time and adds cost to the product.
An electrical wiring device of the present of invention is intended to be attachable to the wires of a cable in the field and rugged enough to withstand the rigors of industrial applications, yet competitive in cost. The present wiring device includes a housing having a generally cylindrical front portion and a rear extension in the general form of a semi-cylinder. As used herein, xe2x80x9cforwardxe2x80x9d or xe2x80x9cdistalxe2x80x9d refers to the portion of a connector which is designed to attach to a mating connector; and the terms xe2x80x9crearxe2x80x9d or xe2x80x9cproximalxe2x80x9d refer to the portion of the connector attached to the cable.
A core is received in the forward portion of the housing. The core carries electrical contact elements, male or female, according to the desired type of connector.
The housing extension receives a clamp member which provides two notable functions. First, it secures the wiring device to a cable providing strain relief for the connections between the wire conductors of the cable and the connector elements of the wiring device. The clamp of the instant invention also secures the core to the housing by means of positive, quick-connect coupling which avoids the use of screws, thus reducing cost and the time of replacement, and improving the appearance of the product.
A first series of truncated walls are formed in the clamp member. The truncated walls are generally straight; and they extend radially inwardly of the clamp member that is, transverse of an axis of the wiring device. A second series of spaced, truncated walls are formed in opposing relation to the truncated walls of the clamp member. The second series of walls is formed in the extension of the core. Each of the truncated walls has a central recess adapted to engage and compress the outer jacket of the cable.
When the clamp is assembled to the housing extension, the threadless quickconnect coupling secures the core to the housing. To accomplish this, the core is provided with a pair of rearwardly extending arms at the proximal ends of which there are apertures. The clamp member is provided with a pair of locating fingers at either end. As will be explained further within, the clamp is reversible in order to accommodate cables of different size. In either assembled state of the clamp, however, a forward pair of locator fingers are received in the rear apertures of the extension arms of the core to lock the core to the housing. This leaves the face of the core free of screw heads, reduces material cost and saves time installing connectors in the field.
Moreover, the opposing pairs of truncated walls are spaced such that the central recesses therein are sized to receive cables of different diameter.
For larger sized cables, the clamp is orientated in a direction that accommodates the pairs of truncated walls which cooperate to force the cable into a serpentine arrangement, bending and compressing the cable to secure it in strain relief relationship with the connector assemblies of the core. For smaller sized cable where the force against which strained relief protection is typically smaller, the clamp compresses the cable inwardly to effect two axially spaced gripping areas, each positively securing the cable to the core to provide strain relief.
Other features and advantages of the present invention will be apparent to persons skilled in the art from the following detailed description of the illustrated embodiment accompanied by the attached drawing wherein identical reference numerals refer to like parts in the various views.